Video monitors comprising cathode-ray tubes (CRT's) are widely used display devices. Color CRT displays are especially useful means for conveying graphic information. Generally, a color CRT display includes three electron guns, each gun controllable to excite an associated red, green or blue phosphor set carried on the CRT screen. In some applications, such as graphic arts, advertising, textile design, etc., color CRT displays are relied upon to display colors having specific colorimetric parameters, so that the identical color can be reproduced with other media (paints, inks, dyes, etc.) using those same colorimetric parameters. Such parameters may be the well-known XYZ tristimulus values as defined by the International Commission on Illumination or CIE.
Disclosed in a copending patent application of Murch, et al., entitled, "Display-Based Color System", is a useful system for organizing colors into a perceptually uniform color space having coordinates that are related to the CIE tristimulus values XYZ. Also disclosed is a method for transforming a point in that color space (as defined by the color space coordinates) into suitable notation for displaying that point (i.e., color) on a CRT display. To this end, the point is transformed into a corresponding rgb intensity vector. An rgb intensity vector is a 3-element vector denoting the relative intensity contribution of each CRT phosphor set required for displaying a selected color. To display a color represented by an rgb intensity vector, it is necessary to convert the rgb intensity vector into associated "DAC values." DAC values are scaled numerical values (usually ranging from 0-255) corresponding to the electron gun control levels required to drive the associated phosphor set at various luminous intensities.
In order to utilize rgb intensity vectors, or for otherwise producing colorimetrically accurate displays, the CRT display must be calibrated. That is, the DAC-value/phosphor intensity relationship must be precisely determined.